TreeModel: removing items will make the expand/collapse button vanish

[ZHawk]

hi,

i have a treemodel which is actually working fine, except removing.
how it looks like:

HEADLINE (expanded view)
 group1
   item1
   item2
   item3
 group2
   itemA
   itemB

HEADLINE (expanded view)
 group1
   item1
   item2
   item3
 group2
   itemA
   itemB

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HEADLINE (collapsed view group1)
 group1
 group2
   itemA
   itemB

HEADLINE (collapsed view group1)
 group1
 group2
   itemA
   itemB

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adding is working fine.
removing items from any expanded group does work fine.

BUT if "group1" is collapsed and i remove an item (eg: "item3"), then the button infront of "group1" will vanish.
i can still press that invisible button to expand "group1".
when i add another item to "group1" the button will appear BUT only if it is expanded.

other groups are not affected until i remove item out of them

bool TreeModel::insertRows( int row , int count , const QModelIndex &parent )
{
	TreeItem *parentItem = getItem(parent);
	beginInsertRows(parent, row, row + count - 1);
	parentItem->appendChild(tmpItem);
	endInsertRows();
	return true;
}
bool TreeModel::removeRows( int row , int count , const QModelIndex &parent )
{
	TreeItem *parentItem = getItem(parent);
	beginRemoveRows(parent, row, row + count - 1);
	parentItem->removeChild(tmpItem);
	endRemoveRows();
	return true;
}

bool TreeModel::insertRows( int row , int count , const QModelIndex &parent )
{
	TreeItem *parentItem = getItem(parent);
	beginInsertRows(parent, row, row + count - 1);
	parentItem->appendChild(tmpItem);
	endInsertRows();
	return true;
}
bool TreeModel::removeRows( int row , int count , const QModelIndex &parent )
{
	TreeItem *parentItem = getItem(parent);
	beginRemoveRows(parent, row, row + count - 1);
	parentItem->removeChild(tmpItem);
	endRemoveRows();
	return true;
}

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any help or ideas ?

[ZHawk]

btw:
just tested it with linux and there it is working fine. the button is a rectangle with a cross inside
i am using win7 and the button is a triangle.